A site for medical students - Practical,Theory,Osce Notes

Alexanders law in Nystagmus - A brief

Nystagmus is a disorder of ocular posture/ mechanisms that maintain steady fixation.

This is characterized by  Biphasic, rhythmic, involuntary, repetitive oscillation of the eyes

What is Alexanders law?

According to the Alexanders law  the amplitude of jerk nystagmus is largest in the gaze of direction of fast component.

  • 1st degree: nystagmus only in the direction of the fast component
  • 2nd degree: nystagmus in primary gaze position
  • 3rd degree: nystagmus in addition to above gazes, also present in the direction of the slow component

How to detect the amplitude of Nystagmus ?

Amplitude is the excursion of the nystagmus and described as

  • Fine: < 5°
  • Moderate: 5°-15°
  • Large: > 15°